Magnetic memory disks, such as the type typically used in a computer hard drive, have a smooth surface over which the read/write head flies during operation. The trend has been to reduce the fly height of the read/write head over the surface of the disk to increase the data recording density on the disk. While it is desirable for a read/write head to fly as close as possible to the surface of the disk, it is important that the read/write head does not contact the disk or defects on the surface of the disk. A defect on the surface of the disk that physically contacts the read/write head may damage the read/write head, the disk, or both. Consequently, care must be taken during the disk processing and testing to assure that there are no defects on the surface of the disk that are greater than the fly height of the read/write head, which today is approximately 1 .mu." (microinch) or less.
Typical magnetic disks include an aluminum, glass, or silicon substrate that is plated with a NiP (nickel phosphate) layer and then textured, e.g., for the contact start stop zone. An underlayer of Cr (chromium) or NiP is sputtered on the plated NiP layer, a thin film of magnetic recording material, typically a Co (cobalt) alloy, is sputtered on the underlayer, followed by the deposition of a protective coating and a lubrication layer. The disk is then burnished to remove any asperities prior to testing the disk to assure the disk meets the required surface specifications. Presently, some magnetic disks are specified to have a roughness less than or equal to about 30 angstroms (3 nanometers).
In conventional methods of burnishing the surfaces of a disk, an abrasive burnishing tape is used. Prior art devices for burnishing a disk with an abrasive tape include the use of air knives and rollers and in some instances the combination of the two. A disadvantage with the use of air knives and rollers is that it is difficult to control the force used to press the burnishing tape against the disk and to ensure that an equal amount of force is applied to both sides of the disk. Without precise control of the force applied to both sides of the disk, one side of the disk may be burnished more than the other. Further, if one side of the disk has a much greater force applied to it than the other, the disk may be damaged. In addition, with air knives it is difficult to control the precise area of the burnishing tape that is pressed against the disk. It is also difficult to burnish with an adequate amount of force without scratching the surface of the disk. Further, rollers are difficult to keep flat against the surface of the disk.